1 // SPDX-License-Identifier: GPL-2.0 2 3 #include <linux/compiler.h> 4 #include <linux/context_tracking.h> 5 #include <linux/errno.h> 6 #include <linux/nospec.h> 7 #include <linux/ptrace.h> 8 #include <linux/syscalls.h> 9 10 #include <asm/daifflags.h> 11 #include <asm/fpsimd.h> 12 #include <asm/syscall.h> 13 #include <asm/thread_info.h> 14 #include <asm/unistd.h> 15 16 long compat_arm_syscall(struct pt_regs *regs, int scno); 17 long sys_ni_syscall(void); 18 19 static long do_ni_syscall(struct pt_regs *regs, int scno) 20 { 21 #ifdef CONFIG_COMPAT 22 long ret; 23 if (is_compat_task()) { 24 ret = compat_arm_syscall(regs, scno); 25 if (ret != -ENOSYS) 26 return ret; 27 } 28 #endif 29 30 return sys_ni_syscall(); 31 } 32 33 static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn) 34 { 35 return syscall_fn(regs); 36 } 37 38 static void invoke_syscall(struct pt_regs *regs, unsigned int scno, 39 unsigned int sc_nr, 40 const syscall_fn_t syscall_table[]) 41 { 42 long ret; 43 44 if (scno < sc_nr) { 45 syscall_fn_t syscall_fn; 46 syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)]; 47 ret = __invoke_syscall(regs, syscall_fn); 48 } else { 49 ret = do_ni_syscall(regs, scno); 50 } 51 52 regs->regs[0] = ret; 53 } 54 55 static inline bool has_syscall_work(unsigned long flags) 56 { 57 return unlikely(flags & _TIF_SYSCALL_WORK); 58 } 59 60 int syscall_trace_enter(struct pt_regs *regs); 61 void syscall_trace_exit(struct pt_regs *regs); 62 63 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, 64 const syscall_fn_t syscall_table[]) 65 { 66 unsigned long flags = current_thread_info()->flags; 67 68 regs->orig_x0 = regs->regs[0]; 69 regs->syscallno = scno; 70 71 local_daif_restore(DAIF_PROCCTX); 72 user_exit(); 73 74 if (has_syscall_work(flags)) { 75 /* set default errno for user-issued syscall(-1) */ 76 if (scno == NO_SYSCALL) 77 regs->regs[0] = -ENOSYS; 78 scno = syscall_trace_enter(regs); 79 if (scno == NO_SYSCALL) 80 goto trace_exit; 81 } 82 83 invoke_syscall(regs, scno, sc_nr, syscall_table); 84 85 /* 86 * The tracing status may have changed under our feet, so we have to 87 * check again. However, if we were tracing entry, then we always trace 88 * exit regardless, as the old entry assembly did. 89 */ 90 if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { 91 local_daif_mask(); 92 flags = current_thread_info()->flags; 93 if (!has_syscall_work(flags)) { 94 /* 95 * We're off to userspace, where interrupts are 96 * always enabled after we restore the flags from 97 * the SPSR. 98 */ 99 trace_hardirqs_on(); 100 return; 101 } 102 local_daif_restore(DAIF_PROCCTX); 103 } 104 105 trace_exit: 106 syscall_trace_exit(regs); 107 } 108 109 static inline void sve_user_discard(void) 110 { 111 if (!system_supports_sve()) 112 return; 113 114 clear_thread_flag(TIF_SVE); 115 116 /* 117 * task_fpsimd_load() won't be called to update CPACR_EL1 in 118 * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only 119 * happens if a context switch or kernel_neon_begin() or context 120 * modification (sigreturn, ptrace) intervenes. 121 * So, ensure that CPACR_EL1 is already correct for the fast-path case. 122 */ 123 sve_user_disable(); 124 } 125 126 asmlinkage void el0_svc_handler(struct pt_regs *regs) 127 { 128 sve_user_discard(); 129 el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table); 130 } 131 132 #ifdef CONFIG_COMPAT 133 asmlinkage void el0_svc_compat_handler(struct pt_regs *regs) 134 { 135 el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls, 136 compat_sys_call_table); 137 } 138 #endif 139